CA2716621A1 - Continuous fuel supply system for a coal gasification reactor - Google Patents

Abstract

The invention relates to a facility for the continuous supply of a coal gasification plant with finely ground fuel material, wherein the fuel is first stored in a storage tank and then fed to a lock hopper system, where it is supplied with gas for the coal gasifica-tion reaction, and the lock hopper system consists of at least two lock hoppers to achieve that the gas is injected quasi-continuously, and the fuel is then passed to a feed tank in which a constant filling level prevails over a given period of time, so that the fuel is conveyed in a constant, smooth and pressurised flow from this feed tank to the burners, the transfer from at least two lock hoppers to a least one feed tank is carried out by pneumatic dense-flow conveying at solid material densities of at least 100 kg/m3 and a differential pressure of at least 0.5 bar so that it is possible to ar-range the facility components at the same geodetic height or different geodetic heights so as to achieve a space saving and flexible plant construction. The invention also relates to a process for the continuous and uniform supply of finely ground fuel to a coal gasification reactor.

Description

Continuous fuel supply system for a coal gasification reactor [0001] The invention relates to a process for the controlled continuous supply of fine-grain to pulverised fuel materials into a pressurised feed tank in a pressure gasifi-cation process in which finely ground or pulverised (< 0.5 mm) fuel materials such as coal, petrol coke, biological waste or fuels are converted in suspension with low particle load (< 50 kg/m3; no fluidised bed) by reaction with gasifying agents containing oxygen, under elevated pressure at temperatures above the slag melting point.

[0002] In the course of pressure gasification processes a carbon-containing fuel material is converted by means of an oxygen-containing gas, wherein the oxygen-l0 containing gas is supplied in a substoichiometric ratio so that a carbon monoxide con-taining product gas is obtained. If the reaction gas contains water vapour, the product gas is of synthesis gas character and contains major portions of hydrogen. To achieve a conversion that is as complete as possible under substoichiometric conditions, the fuel material must be fed to the reactor in finely ground condition. The reaction normally 1s takes place under elevated pressure.

[0003] Since gasification reactions are operated economically only if operated con-tinuously for an extended period of time, the amount of finely ground fuel material sup-plied per time unit should be as constant as possible to ensure trouble-free operation.
The transfer of the fuel material to the required pressure level and the supply of the fuel 20 material under pressure are problems yet to be solved in coal gasification reactions.
For this reason, coal gasification plants always include plant equipment which serve to ensure trouble-free supply of fuel to the reactor. Such equipment usually consists in special dosing tanks and lock hopper assemblies operated by gravity flow.

[0004] Using dosing tanks is not always a means to completely eliminate the pres-25 sure variations occurring when loading the reactor. This may result in pressure varia-tions during the carbon gasification reaction which will temporarily change the composi-tion of the synthesis gas. Especially the discontinuous filling of the dosing tank from the pressure locks generates pressure variations which are of unfavourable effect on the pressure difference which serves as driving force for the conveyance between dosing 30 tank and burner.

[0005] Introducing the fuel material by gravity flow as done when supplying the coal gasification reactors with fuel material is also a potential source of error. As the fi-nely ground fuel material may clog or plug depending on its quality and degree of dry-ing, conveyance will sometimes proceed batchwise only or with unexpected periodic in-terruptions. In addition, lock hopper systems based on gravity flow frequently require sophisticated design solutions since tanks between which conveyance is to be achieved must be arranged on top of each other.

[0006] Fuel feed systems according to the state of the art are expenditure-intensive and not always reliable in operation. In the case of large-capacity plants, the spatial separation of grinding and gasification units involves considerable additional expenditure as regards the transport of finely ground fuel materials from the grinding io unit to the fuel feed system. This makes it necessary to provide additional equipment (conveying vessels or pneumatic pumps, filters, buffer tanks above the feed systems).
In addition, considerable expenditure is incurred by piping, instrumentation and con-struction work, the latter especially because of the exposed position of the buffer tanks at the highest elevation of the gasification unit. Furthermore, lock hopper systems which operate according to the gravity flow principle have proven to be inadequately re-liable in operation. Additional equipment will at any rate increase the risk of failure.

[0007] Apart from this commonly known fact, the principle of lock hopper gravity feed involves specific functional risks. Despite many very diverse approaches, it has proven to be extremely difficult to carry out the process of vessel pressurising carefully enough to keep the internal stress of the bulk material sufficiently low. In many cases, the bulk material is locally compacted to such a degree that the gravity flow to the feed tank is subsequently not induced at all or only to an inadequate extent. The solid mate-rial inventory of the feed tank hence diminishes, which frequently causes a limited out-put or may even cause the failure of the gasification unit.

[0008] The problem aggravates if oversizing owing to a high plant capacity comes up against the construction limits and if the gasification unit is to be designed for a higher pressure (typically 4 MPa) than that of the units which have been in operation for many years (typically 2.5 MPa).

[0009] Lock hopper gravity feed from the lock hopper into the feed tank will pro-duce very high transfer mass flow rates, provided the desired gravity flow is achieved, and thus comparatively short transfer periods. The transfer of solids during lock-hopper feeding will raise the filling level in the feed tank. The filling level will then continuously decrease again by the amounts of fuel supplied to the burners and increase again by the next lock hopper transfer operation. In this way, the feed tank is subjected to tem-porarily changing conditions which may even affect the steady delivery from the feed tank. It is considerably more advantageous to keep the pressure conditions, the filling level and the pulsed feed into the bulk fill by dropping-in material, for instance, as con-stant as possible with regard to time.

[0010] The present invention solves these problems by a dosing tank which con-tains the finely ground fuel material under pressure and, according to the invention, has a nearly constant fuel filling level. Such almost constant filling level in the feed tank is ensured according to the invention by supplying solid material continuously from at least two lock hoppers via at least one jointly used continuous supply line which is suited for dense-flow conveying. As the continuous supply line is not operated by grav-ity, it is further possible to install the feed tank and the supplying lock hoppers at differ-ent geodetic elevations and, in addition, at a greater distance from one another, as may be, for example, in a different building.

[0011] Known are dosing devices for fuel materials that feed the fuel material to the reactor via a dosing tank with upstream lock hopper system. US 5143521 A
de-scribes a system for the feeding of fuel material into a feed tank which stores pressur-ised fuel material and is supplied continuously with finely ground fuel material by a sys-tem of lock hoppers. The lock hoppers are connected by a line and pressurised alter-nately. The pressure of the expansion gas of the one lock hopper may be used via a system of expansion turbines, Venturi tubes and compressors to pressurise the other lock hopper. In this way, it is possible to adjust the pressure of finely ground coal at at-mospheric conditions to a level suited for coal gasification. Nitrogen is used as pressur-ising gas.

[0012] DE 102005047583 Al describes a process and a facility for dosing and feeding pulverised fuel materials under pressure to a coal gasification reactor. To en-sure a constant the feed of fuel material to the coal gasification reactor over a given pe-riod of time, the fuel is stored intermediately in a dosing tank, in the lower part of which a dense fluid bed is generated above the tank bottom by feeding in gas, through which the pulverised fuel material is supplied continuously via burners to a pressurised gasifi-cation reactor. Actual feeding to the burners is here implemented by the so-called high-speed conveyance, wherein the supply of auxiliary gas to the feed line downstream of the burner is used to generate a pressure difference by which the fuel material is then transported to the burners. The dosing tank is supplied with fuel material from two locks which transport the fuel material by means of gravity and a star feeder into the dosing tank. This is, however, susceptible to failures and requires structures of high altitudes.
A use of grinding devices is not mentioned.

[0013] The present invention describes an integrated process for comminuting a carbonaceous fuel material, pressurising the fuel by means of a suitable gas, distribut-ing and transporting the fuel to a feed tank and feeding it to the reactor.
Transport, dis-tribution of the fuel and feeding to the reactor are implemented by dense-flow convey-ing in a so-called continuous supply line. In this way, the complete fuel supply chain of the reactor can be carried out without gravity flow. The gasification reactor outlet tem-peratures are preferably above the slag melting point in a range between 1200 and 2000 C and the pressure is preferably between 0.3 and 8 MPa.

[0014] Dense-flow conveying in this context signifies a pneumatic conveying which does not transport the fuel material particles as individual particles but in a dense flow in the form of dense packings or plugs which fill in the entire cross-sectional area of the pipe. The dense-flow conveying flow rates are generally between 4 and 5 m/s, wherein a high transport volume is achieved despite the high solid load of the gas flow. Dense-flow conveying is characterised by gentle transport of the material and is especially lit-tle susceptible to failures by adhering or moist conveying material. The present pneu-matic dense-flow conveying process is carried out preferably with solid densities of at least 100 kg/m3 and at a differential pressure of at least 0.5 bar.

[0015] Special claim is laid to a process for supplying finely ground fuel materials to a cooled reactor (15) for gasification by means of oxygen-bearing gasifying agents under pressure, wherein = the gasifier outlet temperatures are above the slag melting point in the range between 1200 and 2000 C and the pressure is between 0.3 and 8 MPa, and the finely ground fuel material is pressurised via a lock system to a pres-sure level above the gasifier pressure, transferred to at least one feed tank and from there dosed in dense flow via at least one fuel line to one or more gasification burners of one or several gasifiers, and = the transfer from at least two lock hoppers to at least one feed tank is carried out by using a pneumatic continuous supply line jointly, simultaneously or successively at solid material densities of at least 100 kg/m3 and a differen-tial pressure of at least 0.5 bar.

[0016] In an embodiment of the process, the transfer from the lock hoppers to the feed tank or tanks is controlled by at least one connection device and at least one uni-fying element and the transfer from the unifying element to the feed tank is imple-mented by means of individual connection devices or by means of additional unifying elements with transferring connection devices.

[0017] The transferring connection devices are designed in an exemplary fashion as continuous supply lines suited for dense-flow conveying. By installing unifying ele-ments downstream of the lock hoppers, the fuel material is conveyed from the lock hoppers to the feed tanks via a number of continuous supply lines which is smaller than 1o the number of lock hoppers. It is also possible to direct the solid material from the out-lets of the lock hoppers not directly into the unifying elements but via connection ele-ments so that it is passed via lines into the unifying elements first and then into the con-tinuous supply line. Here, the number of unifying elements is smaller than the number of lock hoppers and it may be identical with the number of continuous supply lines. The unifying elements are provided as closely to the outlet nozzles as possible and ar-ranged as symmetrically to them as possible to ensure a smooth solid flow.

[0018] In a preferred embodiment of the process, the fuel material is processed into a finely ground form by mean of a mill or a suitable grinding device. For this pur-pose, the fuel material can be made available in any form. It is possible to deliver fuel material that has already been finely ground. In such case, claim is only laid to the pressurisation of the fuel material and the transport into the reactor.
Usually, however, the grinding process is an integral part of the process according to the invention, espe-cially if the grinding device is arranged in local proximity to the reactor.
In a preferred embodiment of the invention, the coal milling and drying (CMD) unit is an integral part of the coal gasification plant.

[0019] To carry out the transfer function, the lock hoppers are pressurised with a gas. Recycled process gas may be used, for example. It is also possible to use an inert gas. Pressurising is performed advantageously with inert gases (e.g. nitrogen, carbon dioxide) or by means of process gases or recycle gases. To configure the transfer process in an advantageous way, pressurising of the lock hoppers by supplied gas is preceded by a mutual partial pressurisation of the lock hoppers. To keep the process conditions as constant as possible, the lock hoppers are pressurised and depressur-ised alternately.

[0020] In an additional embodiment of the process, the grinding circuit is blanketed with inert gas and for blanketing the grinding circuit with inert gas, the expansion gases from the lock hoppers are used. The latter are depressurised at regular intervals for carrying out the transfer process, wherein the discharged gas can be recycled to the grinding devices. This will make the process reliable in operation and keep the plant operating cost at a reasonable level. The gas of the grinding circuit is additionally de-dusted. For this purpose a dust separator is used which may also be used to dedust the expansion gases from the lock hoppers. The pressurisation or expansion gas may be dedusted by means of a dust separator in basically any place of the process.

[0021] The finely ground fuel material is then preferably fed to a feed tank.
In this way it is possible to store the fuel material in accordance with the availability and to temporarily buffer the raw material flow. It is thus possible to adjust bottlenecks which are compensated by refilling at a later date.

[0022] To run the process according to the invention, all solid, carbonaceous fuel materials that can be divided into small particles by milling or grinding may be used.
These may especially be all kinds of carbon, wherein hard coal, brown coal and basi-cally coals of all carbonization kinds are suitable. Suitable as fuel materials are also biological fuel materials such as wood, biomasses and other fuel materials such as plastic waste and petrol coke or mixtures of these. To run the process according to the invention, it should merely be possible to crush the fuel materials into a finely ground form which is suitable for dense-flow conveying.

[0023] Subsequent to the comminuting process and the storage in the feed tank, the solid material is passed to the lock hopper system in which the solid material is pressurised with supplied gas to carry out the gasification reaction. In a preferred em-bodiment of the invention the feed tank is atmospheric. Conveyance of the solid mate-rial into the lock hoppers is advantageously performed by gravity.

[0024] To run the process according to the invention, the lock hopper system con-sists of at least two lock hoppers. In this way, it is possible to connect the discharging operations in series and to ensure a nearly continuous material flow. In an advanta-geous embodiment the lock hoppers are pressurised individually.

[0025] In an embodiment of the process according to the invention two lock hop-pers are used to ensure a continuous material flow. The investment cost for the plant is thus low. In a further embodiment of the invention, it is also possible to use three or more lock hoppers. This is especially recommended in the case of high plant through-puts.

[0026] It is possible to use a plurality of lock hoppers and a plurality of unifying elements. In principle, the facility according to the invention may consist of lock hop-pers and unifying elements of any number. The number of lock hoppers is determined by the throughput of the plant. The number of unifying elements is determined by the number of lock hoppers and the number of continuous supply lines. Different arrange-ments of theoretically any number are possible. The interconnection of the lock hop-pers and the unifying elements may basically also be carried out as desired.
For this, any number of connection devices may be used. Preferred connection devices are pipelines. Possible as well are hoses or flanges, for example. The mode of spatial in-terconnection may also be selected as desired.

[0027] Subsequent to pressurising the tanks, the contained fuel material is dis-charged in dosed quantities and the pressure in the tanks is then expanded. In an ad-vantageous embodiment of the invention the expansion gas is used to partially pressur-ise the next lock hopper in the cycle. In order to improve the efficiency, this may be im-plemented by introducing the expansion gas directly into the tank to be pressurised.

[0028] To reduce the dust load of the expansion gas, the expansion gas is advan-tageously introduced into the dust separator which is also used to dedust the gas from the storage tank or from the grinding process. In principle, it is also possible to clean the gas from solid material dusts by means of several independent dust separators. To keep the investment cost low, it is advantageous to use only one dust separator.

[0029] The material flow from the lock hoppers is routed to the feed tank via at least one unifying element and the continuous supply line. To utilise the advantage of the invention, the lock hoppers are emptied one after the other in such a way that a nearly continuous fuel material flow to the feed tank is achieved. In this way, the sub-sequent feed tank for the gasification reactor can be supplied with a continuous mate-rial flow of a pressure that is suitable for the gasification reaction, wherein the filling level of the feed tank remains nearly constant. The filling level of fuel material in the feed tank can be adjusted according to the advantageous embodiment of the process such that it does not vary by more than 30 % over a given period of time. If the proc-ess according to the invention is run by specialists, it is easily possible to keep the fill-ing level variations of the feed tank in a range of not more than 10 % over an ex-tended period of time.

[0030] The filling level of the feed tank may also be kept constant by controlling the continuous supply of finely ground fuel material from the lock hoppers by adjusting the pressure difference between lock hopper and feed tank. The inlet or outlet of gas into the free space of the lock hoppers influences the pressure difference between lock hopper and feed tank and is used as control parameter for the solid material transport.

[0031] To run the process, the finely ground fuel materials are preferably of a par-ticle size which is smaller than 0.5 mm. This is achieved in a grinding and comminuting process. The discharge of solid material from the lock hopper may be facilitated by the addition of gas into the lock hopper in the immediate vicinity of the discharge nozzle.
The density in the continuous supply line is adjusted advantageously by adding gas into the continuous supply line or into the unifying element or into both. The addition of gas at this point may also be used to purge the continuous supply line or the unifying element. The connection elements between lock hopper and unifying element may also be supplied with gas.

[0032] The conveying gas volume supplied at the discharge of the lock hopper is recovered in the feed tank in an advantageous embodiment of the invention and re-turned into the lock hopper by means of an injector. The returned conveying gas and the propellant gas of the injector are jointly used as replacement gas for the emptying lock hopper and thus also for maintaining the pressure of the lock hopper during the conveying process.

[0033] To suit certain requirements, it may be of advantage that two or more lock hoppers discharge solid material simultaneously or temporarily simultaneously into a conveying line. Gas balancing between the feed hoppers may advantageously be achieved by a gas connection line between the lock hoppers.

[0034] The process according to the invention may also include processes which are subsequent processes of the coal gasification process according to the invention.
Also included in the process according to the invention are process steps which are re-quired for a routine operation of the reactor. These may, for instance, be cleaning steps. These may as well be supporting process steps such as the supply of gas for loosening plugs. Possible as well are process steps for measuring parameters such as filling levels, flow rates, pressures or temperature. The invention especially also de-scribes a facility to run this process. The facility according to the invention may include all plant units that are required for operating a coal gasification plant according to the process of the present invention.

[0035] Claim is also laid to a facility used to supply solid fuel materials to a reactor for the gasification of solid fuel materials, comprising = a grinding device, = a dust separator, = a storage tank, = at least two lock hoppers, = at least one connection device for dense-flow conveying, = a feed tank, = a gasification reactor, wherein = the grinding device is connected to a storage vessel by means of connection devices, wherein a dust separator is installed between the grinding device and the storage tank, and = the storage vessel is connected to the lock hoppers via connection devices which are suited for gravity flow or dense-flow conveying, and = the lock hoppers are connected to a feed tank by means of jointly used connec-tion devices which are suited as continuous supply line for dense-flow convey-ing, and this feed tank is connected to the gasification reactor via further fuel material lines.

[0036] The dense-flow conveying from the lock hopper system to the feed tank al-lows to install the feed tank at the same or different geodetic height as the lock hopper system. In the case of the gravity lock hopper systems known to date it is indispensa-ble to install the lock hoppers above the feed tank. By this measure it is possible to re-duce the constructional height of the overall plant to a considerable degree.
It is also possible to locate the lock hopper system and the feed tank and the reactor in separate buildings. The invention also involves the advantage that lower constructional heights may be selected for the respective units. The various plant components may be ar-ranged as desired so that the spatial layout of the plant can be done in a flexible way.

[0037] The transfer of the fuel material from the lock hoppers to the feed tank or tanks is implemented via at least one connection device and at least one unifying ele-ment, and the transfer from the unifying element to the feed tank via individual continu-ous supply lines for dense-flow conveying. The transfer from the lock hopper to the feed tank may be implemented via further unifying elements with transferring connec-tion devices.

[0038] Depending on the embodiment of the process, 2 or more lock hoppers are used to pressurise the fuel material. This is especially recommended for plants with high fuel material throughputs or if the lock hopper system is to be pressurised to higher pressures. The inlet sides of the lock hoppers are connected to a feed tank which conveys the fuel material into the lock hoppers by the aid of both dense-flow conveying and gravity conveying. For this purpose, a star feeder or a material manifold may be installed in a suitable place between the storage tank and the lock hoppers. It is also possible to install intermediate vessels, bulb-shaped vessels or gas feeding de-vices between the storage tank and the lock hoppers.

[0039] The fuel material supply system of the coal gasification plant may also in-clude a grinding device or a mill which may be of any type desired. The mill in turn may also include additional comminuting devices such as shredders for wood or crushers for coal. The mill or crusher may also be supplied with gas or blanketed with inert gas.
In a preferred embodiment of the facility according to the invention the lock hoppers are spatially integrated into the grinding unit and are filled by gravity flow from at least one storage vessel for finely ground fuel.

[0040] To run the process according to the invention, the lock hopper system con-sists of two or more lock hoppers which may be pressurised from outside. The lock hopper system is connected to an upstream storage tank which supplies the lock hop-per system by gravity conveyance with finely ground fuel material. The conveying or transport of the solid material is influenced advantageously by introducing gas so that gas introduction devices which influence the conveying or transport of solid material may be installed in any place of the lock hopper system, the dense-flow conveying lines or the feed tank.

[0041] The lock hoppers may be of any design desired. They may be provided in the form of cylinders or as spheres. Preferably they are provided with a downward dis-charge cone, the angle of which is determined by the properties of the bulk material to counteract arching and to ensure a uniform material flow. For this reason, they are ta-pered towards the bottom in the ideal case. The fuel material hence exits downwards in gravity direction. The storage tanks as well as the downstream feed tanks are also of this preferred design. The lock hoppers are fitted with inlet valves via which the lock hoppers may be pressurised. The lock hoppers are equipped with nozzles, shutoff and control valves according to the state of the art which serve to control the flow of solid material, to depressurise and pressurise or carry out pressure compensation.

[0042] In an advantageous embodiment of the invention the expanded gases may be recycled to the grinding device and/or the fuel storage tank. To separate the gas from dust before it is discharged from the system or recycled for being used in the plant, the lines are preferably routed via dust separators. The latter separate the dust and pass it to a proper disposal or recycle it to the storage tank, for example. It is theo-retically possible to install devices by which the gas flow can be separated from solid material or dust in any place of the lock hopper system, the dense-flow conveying line, the fuel lines or the expansion lines. It is therefore of advantage to provide for a gas-sided connection of the lock hoppers with the feed tank.

[0043] The lines may be provided with gas introduction devices in any place de-sired. These may be so-called "boosters", for example. Especially the discharge de-vices for solid material, however, which are prone to caking, plugging or arching, may include additional gas introduction devices by which the solid material can be loosened.
The lock hoppers as well may be provided with gas introduction devices in any place desired.

[0044] In such case, the material discharge of the lock hoppers is fitted with a connection element via which the material flow from the lock hoppers is passed to the unifying element. These elements shall be designed for high pressures as the fuel is at a pressure level above that of the gasification reactor during the whole conveying proc-ess from the lock hopper to the feed tank. To ensure controlled material flow, the lock hoppers are mounted advantageously such that they are arranged symmetrically to the unifying element so that the connection elements between the lock hoppers and the unifying element are preferably of the same length.

[0045] The unifying elements may be of any type desired. Preferably these are devices which assume the function of mixing elements. These may be, for example, pipe manifolds or Y-manifolds but also so-called "pipe headers". Examples of suitable unifying elements are given in EP 340419 B1; here the elements described are re-versed in their function and used as unifying elements. The connection devices as well may be of any type desired. Preferably used are pipes. Possible as well are hoses or flanges.

[0046] The connection devices or the unifying element may also be supplied ad-vantageously with gas for material distribution. If a plurality of unifying elements is pro-vided, they may be supplied with gas individually. For this purpose, the unifying ele-ment is preferably provided with a gas introduction device. The feed tank as well is pro-vided with gas injection devices or gas introduction devices in an embodiment of the invention.

io [0047] The pipeline for supplying solid material to the feed tank normally ends a-bove the solid material filling level and, depending on the properties of the bulk mate-rial, it may also enter the feed tank below the solid material level in an embodiment of the invention. As the solid material level is subject to only slight variations if the process is run advantageously, this may be at a lower or central height position of the feed tank.
In this way it is possible to achieve a low bulk density in the feed tank if the solid mate-rial shows good gas-retaining properties, which reduces the additional amount of gas required for conveyance to the burners.

[0048] The facility according to the invention may be provided with plant equip-ment required for the operation of a solid fuel supply system in any place desired. This may be pumps but may also be heating or cooling devices. Also included are valves or shutoff devices. These may theoretically be installed in any place. The integration of in-jectors is also possible. Here, so-called "boosters" (gas injectors) may be used, for ex-ample, but also possible are gas jet pumps. Finally the facility according to the inven-tion also includes thermometers or flow sensors for gases and solid materials, pressure sensors, level meters or other measuring devices.

[0049] The design type of dense-flow conveying from the lock hoppers and from the feed tank allows to construct the whole plant construction at low height.
As the con-veyance is independent of gravity, the plant equipment may be installed in any place desired. By this system, the space requirement can be reduced to a considerable de-gree. The system of several lock hoppers and the upstream storage tank as well as the constant-level feed tank allows to achieve trouble-free and very constant conveying of fuel to the feed tank over a given period of time, even for an extended period of time.
This contributes to the reliability of the plant and ensures a constantly high product quality.

[0050] The facility according to the invention is illustrated in more detail by means of two drawings, the embodiment not being limited to these drawings.

[0051] FIG. 1 shows the process flow of a coal gasification plant which is equipped with a facility for the supply of fuel material according to the invention.
Fuel material 1 is supplied and introduced into a mill or suitable grinding device 2. The finely ground fuel material is then passed via a dust separator 3 and fuel line 3a into a storage tank 4, where the fuel is stored intermediately. Subsequently the fuel is supplied to lock hop-pers 5. The represented example shows two of them 5a, 5b. Lock hoppers 5 serve to pressurise the fuel batch by batch by supplying gas. For this purpose, lock hoppers 5 are provided with gas introduction devices 6a, 6b above the filling and gas introduction devices 6'a, 6'b into the filling. Between lock hoppers 5 there is a compensation line 7 which may be opened in the case of need. An expansion line 8 for depressurisation leaves lock hoppers 5, via which the expanded gas may be used completely or only partially for blanketing grinding device 2. The expanded gas, however, may also be used for blanketing storage tank 4 with inert gas. To adjust recycle gas 8c of grinding device 2 recycled by means of blower 8b to adequate temperatures, the line may be provided with a heat exchanger 8d or another suitable device for supplying heat.
Downstream of lock hoppers 5a, 5b the finely ground fuel material is discharged via suitable connection devices 9a, 9b and passed to unifying element 10. Unifying ele-ment 10 may be supplied with gas via gas line 11. The finely ground material is then routed via continuous supply line 12 to a feed tank 13.

[0052] In the exemplary variant shown in FIG. 1, two lock hoppers 5a, 5b make use of a continuous supply line 12 via unifying element 10. This is achieved advanta-geously in such a way that lock hoppers 5a, 5b feed the solid material alternately into dense-flow conveying continuous supply line 12 via unifying element 10. To minimise the interim time for switching from one lock hopper to the other 5a, 5b and to ensure an almost uninterrupted conveying of solid material, it is advantageous to couple both lock hoppers 5a, 5b in timely overlapping manner to unifying element 10. Helpful in this re-spect is pressure compensation via compensation line 7 between that lock hopper that is almost empty already and the other lock hopper that is still full 5a, 5b.
It goes without saying that it is also possible and advantageous to implement the described procedure with more than two lock hoppers 5. If there are more than two lock hoppers 5, it is also possible to use the expansion gas of that lock hopper 5 that has just been emptied and shall now be depressurised for being loaded with solid material from atmospheric stor-age tank 4, for partial pressurisation of a lock hopper 5 which is still under atmospheric condition. Connection device 9a, 9b is provided with two valves (not shown), one close to the hopper discharge, one close to unifying element 10. After a lock hopper 5 has been emptied to a minimum level and shut off from unifying element 10 by the valve in proximity to unifying element 10, it is recommended to purge or blow free by gas injec-tion 9'a, 9'b at connection device 9a, 9b, before the second valve is closed.

[0053] In the ideal case, a constant filling level 13a prevails in feed tank 13. The pressure of feed tank 13 can be kept constant by excess gas 21 or feed gas 22 by a gas compensation process. From feed tank 13, the solid material is routed via fuel li-nes 14a, 14b to coal gasification reactor 15 with one or more burners 16a, 16b. In this io case, the entire facility for the supply of solid fuel is located in a separate plant unit, the building of grinding unit 17a. Coal gasification reactor 15 and feed tank 13 are located in another building, the building of gas production unit 17b.

[0054] The advantages of the invention already mentioned which especially in-volve a considerable reduction of the number of equipment items, the construction height and hence the investment cost as well as an increase in plant reliability, are ob-tained for a moderate increase in the demand for pressurising gas. This is due to the fact that that part of the gas used for dense-flow conveying of the solid material in con-tinuous supply line 12 which has been used to reduce the solid material density to a value below the one prevailing in feed tank 13, cannot be used as feed gas for coal gasification reactor 15 since it is excess gas, see FIG. 2. If no additional devices are available, this part is to be removed unused as excess gas 21. At the same time, many times the amount of gas is required in lock hopper 5, which is the active transferring hopper, as a replacement for the discharged amount of solid material. It therefore sug-gests itself to reduce the demand for gas by recycling excess gas 21 from feed tank 13 as recycle gas 20 to the lock hopper and using it for a partial substitution of the gas consumed for replacement. This may be implemented by a blower or another device for pressure increase. Owing to the low pressure difference to be overcome between feed tank 13 and lock hopper 5 at simultaneously high system pressure, an injector 18 suggests itself, especially a gas jet pump. In addition, the pump is also capable of con-veying dust-bearing gas, dust separation is not required. As propellant gas serves the pressurising gas used for the purpose of replacement, which is available at significantly higher pressure. The pressure side of injector 18 is switched over to the currently ac-tive lock hopper 5. Under typical operating conditions the portion of recycle gas amounts to about 25% of the amount of replacement gas. At the same time the supply pressure of propellant gas 23 is about 10 bar higher than the pressure of the lock hop-per, whereas the pressure of recycle gas 20 is only about 1-2 bar above the pressure of the lock hopper. These numerical relationships make it obvious to the specialist that injector system 18 is fully operative under the specified conditions.

[0055] Gas recycling is integrated into the pressure control system of feed tank 13 in the following way: Based on the consideration that, at constant operating conditions, excess gas 21 is to be removed from feed tank 13, the pressure increase in feed tank 13 is avoided by having injector 18 suck off the released amount of gas and feed it to lock hopper 5. If the pressure in feed tank 13 continues to rise, the excessive pres-sure amount is removed as excess gas 21. This gas as well can be used beneficially if required, e.g. for substituting purge gases which are fed to the gasification reactor in various places. Should a pressure increase of feed tank 13 be required especially dur-ing the start-up procedure, which cannot be achieved by excess gas 21, with closed valves in the lines for recycle gas 20 and excess gas 21, the shortage is compensated by fresh feed gas 22.

[0056] The pressurising gas used as propellant gas 23 for injector 18 is compen-sation-controlled by the pressure controller of lock hopper 5. Depending on the position of the throttling valve in the propellant gas line, the amount of propellant gas ranges be-tween 70 and 100% of the gas amount required for replacement. The set value of the lock hopper pressure is determined via a cascade (not shown) from the level of feed tank 13 (or from its weight). With regard to the level, a fixed set value (e.g. 50%) is given. If this set value is exceeded, the value of pressure difference between lock hop-per 5 and feed tank 13 controlled by the controller cascade is reduced so that the sub-sequently fed solid mass flow decreases, and if the level drops below the set value, the controllers operate vice versa.

[0057] Fig. 3 to 8 show, by way of example, arrangements with a varying number of lock hoppers 5 and unifying elements 10. These are connected by pipelines in differ-ent ways.

[0058] FIG. 3 shows a facility according to the invention which includes three lock hoppers 5 and one unifying element 10, wherein each lock hopper 5 is connected to unifying element 10 via a connection device 9, and unifying element 10 is connected to feed tank 13 via a continuous supply line 12. Unifying element 10 can be supplied with gas via gas line 11.

[0059] FIG. 4 shows a facility according to the invention which includes three lock hoppers 5 and two unifying elements 10, wherein two lock hoppers 5 are connected to the first unifying element 10a via connection devices 9a, 9b, and the first unifying ele-ment 10a is connected to the second unifying element 10b via another connection de-vice, and the third lock hopper 5 is directly connected to the second unifying ele-ment 10b via a connection device 9c, and the second unifying element 10b is con-nected to feed tank 13 via a continuous supply line 12.

[0060] FIG. 5 shows a facility according to the invention which includes four lock hoppers 5 and three unifying elements 10, wherein two lock hoppers 5 each are con-nected to one unifying element 10 each via connection devices 9a-9d, these unifying elements 10 being connected to the third unifying element 10c via further connection elements 9e, 9f, and the third unifying element 10c being connected to feed tank 13 via a continuous supply line 12.

[0061] FIG. 6 shows a facility according to the invention which includes six lock hoppers 5 and two unifying elements 10, wherein three lock hoppers 5 each are con-nected to one unifying element 10 each via connection devices 9, these unifying ele-ments 10 being connected to feed tank 13 via separate continuous supply lines 12a, 12b.

[0062] FIG. 7 shows a facility according to the invention which includes eight lock hoppers 5 and two unifying elements 10, wherein four lock hoppers 5 each are con-nected to one unifying element 10 each via connection devices 9a, 9b, these unifying elements 10 being connected to feed tank 13 via separate continuous supply lines 12.
[0063] FIG. 8 shows a facility according to the invention which includes eight lock hoppers 5 and three unifying elements 10, wherein four lock hoppers 5 each are con-nected to one unifying element 10a, 10b via connection devices 9, these unifying ele-ments 10a, 10b being connected to the third unifying element 10c via further connec-tion devices 9, and the third unifying element 10b being connected to feed tank 13 via a continuous supply line 12.

[0064] List of references used 1 Fuel material 2 Grinding device 3 Dust separator 3a Fuel line 4 Storage tank 5,5a,5b Lock hoppers 6,6a,6b Gas introduction devices 6'a,6'b Gas introduction devices 7 Compensation line 8 Expansion line 8a Expansion gas line 8b Blower 8c Recycle gas 8d Heat exchanger 9a-9f Connection devices 9'a,9'b Gas injection 10, 10a-10c Unifying elements 11 Gas line 12, 12a, 12b Continuous supply line 13 Feed tank 13a Filling level 14a,14b Fuel lines 15 Coal gasification reactor 16a,16b Burners 17a Building of grinding unit 17b Building of gas production unit 18 Injector 19 Gas 20 Recycle gas 21 Excess gas 22 Feed gas 23 Propellant gas Ap Pressure as control parameter PC Pressure controllers

Claims (35)

1 claims 1. Facility used to supply solid fuel materials to a reactor for the gasification of solid fuel materials, comprising .cndot. a grinding device (2), .cndot. a dust separator (3), .cndot. a storage tank (4), .cndot. at least two lock hoppers (5), .cndot. one connection device (12) for dense-flow conveying, .cndot. a feed tank (13), .cndot. a gasification reactor15), wherein .cndot. the grinding device (2) is connected to a storage tank (4) by means of connec-tion devices, wherein a dust separator (3) is installed between the grinding de-vice (2) and the storage tank (4), characterised in that .cndot. a device for pressure increase (18) is provided which returns conveying gas from feed tank (13) to lock hopper (5), .cndot. the storage tank (4) is connected to the lock hoppers (5) via connection devices which are suited for gravity flow or dense-flow conveying, and .cndot. the lock hoppers (5) are connected to a feed tank (13) by means of jointly used connection devices (12) which are suited as continuous supply line (12) for dense-flow conveying, and this feed tank is connected to the gasification reac-tor (15) via further fuel lines (14).

2. Facility according to claim 1, characterised in that the transfer of the fuel material from lock hoppers (5) to feed tank or tanks (13) is implemented via at least one connection device (9) and at least one unifying element (10), and the transfer from unifying element (10) to feed tank (13) via individual continuous supply lines (12) for dense-flow conveying or via other unifying elements (10) with transferring con-nection devices (9e,f).

3. Facility according to claim 2, characterised in that the facility includes three lock hoppers (5) and a unifying element (10), wherein each lock hopper (5) is con-nected to unifying element (10) via a connection device (9), and unifying ele-ment (10) is connected to feed tank (13) via a further connection device (12).

4. Facility according to claim 2, characterised in that the facility includes three lock hoppers (5) and two unifying elements (10), wherein two lock hoppers (5) are con-nected to the first unifying element (10a) via connection devices (9a, 9b), and the first unifying element (10a) is connected to the second unifying element (10b) via another connection device (9c), and the third lock hopper (5) is directly connected to the second unifying element (10b) via a connection device, and the second uni-fying element (10b) is connected to feed tank (13) via a further connection de-vice (12).

5. Facility according to claim 2, characterised in that the facility includes four lock hoppers (5) and three unifying elements (10), wherein two lock hoppers (5) each are connected to one unifying element (10) each via connection devices (9a-9d), these unifying elements (10) being connected to the third unifying element (10c) via further connection elements (9e, 9f), and the third unifying element (10c) being connected to feed tank (13) via a further connection device (12).

6. Facility according to claim 2, characterised in that the facility includes six lock hoppers (5) and two unifying elements (10), wherein three lock hoppers (5) each are connected to one unifying element (10) each via connection devices (9), these unifying elements (10) being connected to feed tank (13) via separate connection devices (12a, 12b).

7. Facility according to claim 2, characterised in that the facility includes eight lock hoppers (5) and two unifying elements (10), wherein four lock hoppers (5) each are connected to one unifying element (10) each via connection devices (9), these uni-fying elements (10) being connected to feed tank (13) via separate connection de-vices (12).

8. Facility according to claim 2, characterised in that the facility includes eight lock hoppers (5) and three unifying elements (10), wherein four lock hoppers (5) each are connected to one unifying element (10a, 10b) each via connection devices (9), these unifying elements (10a, 10b) being connected to the third unifying ele-ment (10b) via further connection devices (9), and the third unifying element (10b) being connected to feed tank (13) via a further connection device (12).

9. Facility according to any of the claims 1 to 8, characterised in that the lock hop-pers (5a, 5b) are spatially integrated into grinding unit (1) and are loaded from at least one storage tank (4) for finely ground dried fuel material.

10. Facility according to any of the claims 1 to 9, characterised in that the lock hop-per system (5) consists of two or more lock hoppers which may be pressurised from outside.

11. Facility according to claim 1, characterised in that the lock hopper system (5) is connected to a downstream storage tank (4) which supplies the lock hopper sys-tem by gravity conveyance with finely ground fuel material.

12. Facility according to any of the claims 1 to 11, characterised in that the gas side of lock hoppers (5) and feed tank (13) is connected by at least one connection line (20).

13. Facility according to any of the claims 1 to 12, characterised in that one or more gas introduction devices may be installed in any place of the lock hopper sys-tem (5), the dense-flow conveying lines, the gas-sided connection lines (20) or the feed tank (13), by which it is possible to influence the conveyance or transport of solid material.

14. Device for the introduction of gas according to claim 13, characterised in that at least one of the gas introduction devices is an injector (18).

15. Facility according to any of the claims 1 to 14, characterised in that devices may be installed in any place of the lock hopper system (5), the expansion lines (7,8,8a), the recycle lines (20) or the excess gas lines (21) by which the gas flow can be separated from solid material or dust.

16. Process for supplying finely ground fuel materials to a cooled reactor (15) for gasi-fication with oxygen-containing gasifying agents under pressure, wherein .cndot. the gasifier outlet temperatures are above the slag melting point in the range between 1200 and 2000°C and the pressure is between 0.3 and 8 MPa, .cndot. and the finely ground fuel material is pressurised via a lock hopper system (5) to a pressure level above the gasifier pressure, transferred to at least one feed tank (13) and from there dosed in dense flow via at least one fuel line (14) to one or more gasification burners (16) of one or several gasifiers (15), and characterised in that .cndot. the conveying gas volume (6'a,6'b) supplied at the discharge of lock hopper (5) is recovered in feed tank (13) and returned to lock hopper (5) by means of a device for pressure increase, .cndot. the transfer from at least two lock hoppers (5a, 5b) to at least one feed tank (13) is carried out by using a pneumatic continuous supply line jointly, simul-taneously or successively at solid material densities of at least 100 kg/m3 and a differential pressure of at least 0.5 bar.

17. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that the expansion gases (8) from lock hoppers (5) are at least partially used for blanketing the grinding circuit with inert gas.

18. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that the dust separator (3) of the grinding unit is also used for dedusting expansion gases (8a) from lock hoppers (5).

19. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that pressurising by supplied gas (6a, 6b) is preceded by a mutual par-tial pressurisation of lock hoppers (5a, 5b).

20. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that the fuel material is conveyed from lock hoppers (5) to feed tanks (13) via a number of continuous supply lines (12) which is smaller than the number of lock hoppers (5).

21. Process for supplying finely ground fuel materials according to any of the claims 16 to 20, characterised in that the solid material from the outlet of each lock hopper (5) is passed to unifying elements (10) via a connection device (9a, 9b) and then into the continuous supply line (12), the number of unifying elements being smaller than the number of lock hoppers and at least identical with the number of continu-ous supply lines.

22. Process for supplying finely ground fuel materials according to any of the claims 16 to 21, characterised in that the unifying elements (10) are provided as closely to and preferably symmetrically to the outlet nozzles of lock hoppers (5).

23. Process for supplying finely ground fuel materials according to any of the claims 16 to 22, characterised in that temporarily at least two lock hoppers (5) discharge solid material simultaneously into continuous supply line (12).

24. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that the feed tank (13) is spatially integrated into the building of the grinding unit.

25. Process for supplying finely ground fuel materials according to any of the claims 16 to 22, characterised in that the geodetic installation height of lock hoppers (5) is smaller than the installation height of feed tank (13).

26. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that the continuous supply line (12) enters feed tank (13) below the solid material level..

27. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that the particle size of the solid fine-grain fuel materials is smaller than 0.5 mm.

28. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that continuous supply from lock hoppers (5) is controlled by adjusting the pressure difference between lock hopper and feed tank such that the filling level of feed tank (13) is kept constant.

29. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that the gas inlet or outlet (6a,6b) into the free space of the lock hop-pers influences the pressure difference between lock hopper (5) and feed tank (13) and is used as control parameter for the transport of solid material.

30. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that the discharge of solid material is facilitated by the addition of gas (6'a, 6'b) into the lock hopper in immediate vicinity to the discharge nozzle.

31. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that the density in continuous supply line (12) is adjusted by adding gas (11) into continuous supply line (12) and/or unifying element (10).

32. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that the continuous supply line (12) can be purged by adding gas (9'a, 9'b) into continuous supply line (12) itself and/or into unifying element (10).

33. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that the connection elements (9a, 9b) between lock hopper (5) and uni-fying element are supplied with gas (9'a, 9'b).

34. Process for supplying finely ground fuel materials according to claim 16, charac-terised in that the conveying gas volume (6'a,6'b) supplied at the discharge of lock hopper (5) is recovered in feed tank (13) and returned to lock hopper (5) by means of an injector (18).

35. Process for supplying finely ground fuel materials according to claim 33 or 34, character-ised in that the propellant gas (23) which serves to control the pressure of lock hopper (5) is used to operate injector (18).